Bevelled knife blade grinding



Aug. 23, 1955 c. A. JOHNSON BEVELLED KNIFE BLADE GRINDING 6 Sheets-Sheet1 Filed Jan. 31, 1951 1y M1414 k m vl llll II Aug. 23, 1955 c. A.JOHNSON 2,715,801

BEVELLED KNIFE BLADE GRINDING Filed Jan. 31, 1951 6 Sheets-Sheet 21521213824302 Coaafl J1 Jofuwon,

Aug. 23, 1955 c. A. JOHNSON BEVELLEZD KNIFE BLADE GRINDING 6Sheets-Sheet 3 Filed Jan. 31, 1951 l i EFF- ILL.

[T I L 3, 1955 c. A. JOHNSON 2,715,801

BEVELLED KNIFE BLADE GRINDING Filed Jan. 51, 1951 6 Sheets-Sheet 4 IIEii\\\\\'!2//// wgmfi (O W; Q] r Q 5 \L 7 a i kw \\?\lll A i'i 13209223023; WWAIO ow,

Aug. 23, 1955 c. A. JOHNSON BEVELLED KNIFE BLADE GRINDING 6 SheetsSheet5 Filed Jan. 31, 1951 (F202 MIN! oiwow, V 611L61 l x l Aug. 23, 1955 c.A. JOHNSON BEVELLED KNIFE BLADE GRINDING 6 Sheets-Sheet 6 Filed Jan. 51,1951 United States Patent BEVELLED KNIFE BLADE GRINDING Charles A.Johnson, Berlin, N. H.

Application January 31, 1951, Serial No. 208,729

9 Claims. (Cl. 51-122) This invention relates to grinding and morespecifically to a machine and method for grinding a fiat-surfacedmaterial to provide a surface which intersects the fiat surface of thematerial along a straight line at an angle which varies progressivelyalong the line of intersection.

A rigid material supplied with such interrelated surfaces meeting at anacute progressively varying angle (hereinafter referred to as the angleof bevel) forms a knifesharpened along the line of surface intersectionto form a cutting edgehighly useful in log chipping in the pulpindustry, where the knife or several such knives are mounted on arotating disc with the cutting edge of each projecting beyond the faceof the disc and extending along a line tangent to a circle having as anaxis the axis of the disc, for cutting logs fed end-on into the path ofthe rotating knives at an angle to the face of the disc.

Such a knife, its method of mounting and the advantages of the resultingcuts produced in logs fed to a log chipper provided with such knives aredescribed and claimed in my co-pending application Serial No. 117,676filed September 24, 1949, now Patent No. 2,655,319, dated October 13,1953.

A specific object of this invention, therefore, is the production of agrinding machine useful for the initial production and subsequentmaintenance of such log chipping knives.

In general, a grinding machine of this invention comprises a shaft forrotatably supporting a grinding wheel and a work holder mounted adjacentthe end of the shaft, the grinding wheel and work holder having inaddition to the relative movement caused by the rotation of the grindingwheel shaft, three other relative movements including (a) reciprocationtowards and away from each other, (b) transverse reciprocation and (c)rotation about an axis extending in the direction of the path oftransverse reciprocation (b). In the simplest form of the machine therotation axis (0) is parallel to the path of reciprocation (b); but in arefined version of the machine, provision is made for having therelative rotation (0) about an axis which, permanently or by adjustment,is not parallel to the path of reciprocation (b), but, though extendingin the same direction, is inclined relative thereto.

The relative movement (a) permits the grinding to proceed progressivelyinto a'work piece held in the work holder. The relative movement (b)permits the grinding to take place back and forth along the length ofthe work piece and the rotation (c) is responsible for varying the angleof the bevel of the cutting edge along its length.

Structure for accomplishing these movements are shown in, and theresults of coaction of the parts are illustrated by, the accompanyingdrawings wherein:

Fig. 1 is a plan view of the parallel rotation axis type machine;

Fig. 2 is a front elevation thereof;

Fig. 3 is an end elevation;

2,715,801 Patented Aug. 23, 1955 Fig. 4 is a vertical section takenalong the line 44 of Fig. 1;

Fig. 5 is an enlarged detail cross-sectional view taken along the line55 of Fig. 2;

Fig. 6 is an isometric view of a work piece ground on the apparatus;

Fig. 7 is a front elevation of a refined version of the machine;

Fig. 8 is a detail inside View of a part of the apparatus of Fig. 7;

Fig. 9 is a plan view of the detail of Fig. 8;

Fig. 10 is a schematic illustration of a knife chipper; and

Figs. 11 and 12 are graphical illustrations of certain relations betweenthe knife, the grinder and the chipper as will be hereinafter described.

The apparatus comprises a conventional base 10 having mounted thereon areciprocating carriage 12 which carries at each end thereof an upright14 containing bearings 15, in which are journalled the trunnions 16 of awork holder 20 in such manner that the trunnions have a common axisextending in the direction of the path of reciprocating carriage 12 and,in the embodiment of Figs. l6, inclusive, being shown parallel thereto.At the right-hand end of the work holder an upstanding member 22 hasfixed to it, as more clearly shown in Fig. 5, control arm 24 whichextends towards the front of the machine and carries on its end arotatable cam follower 26 which bears against a bar 28, forming a camtrack extending in the same direction as the path of carriagereciprocation. The ends of the track 2% are supported respectively atpivotal connections 29 on uprights 3t and 32. These uprights 3i and 32may be mounted on the base of the apparatus for independent slidablevertical adjustment relative thereto to vary the slope of the cam track28 relative to the base and path of carriage reciprocation.

It will, therefore, be understood that the motion of the knife holder 20about the common axis of its trunnions 16 under the influence of gravityis resisted and limited by the cam track 28 to an extent depending uponthe particular longitudinal position of the cam follower 26 on the camtrack 28 as results from the particular position of the carriage 12 inits reciprocation relative to the base 10.

The work holder 20 is provided with fastening means such as bolts 40,retainer plates 42 and nuts 44 for retaining against the upper surfaceof the holder a work piece A to be ground. In the form shown in thedrawings, this work piece A is of uniform thickness having a flat uppersurface a and provided with three re-entrant recesses 12 along its backedge and through which recesses one or more of the bolts may extend tohold the work piece A firmly against the upper surface of the workholder.

Moreover, the work holder 20 is so designed with respect to thethickness of the work piece A so that it may be positioned in the workholder with its upper surface a extending exactly through the commonaxis of the work holder trunnions 16.

A cup-shaped grinding wheel is mounted on a shaft 52 for rotation in avertical plane which, though nearly parallel to the path ofreciprocation of the carriage 12, is not exactly so but is at a slightangle thereto so that only one side of the wheel 50 actually bearsagainst the work piece to do the grinding.

The shaft 52 is connected by suitable pulleys 53 and belting to themotor 54 and the assembly of shaft 52 and motor 54 is mounted on a slide55 held on base 10 in guideways 56 for reciprocation towards and awayfrom the work holder 20 by means of operation-of the hand wheel 60extending at the front of the machine and 3 r V connected'by suitableconventional means, including a shaft 61 threaded through a block 62depending from slide 55, 'to slide 55.

' There are also provided on the frontface of the carriage 12, two'abutments 70 and'71, which, in th eir paths oftravelwith reciprocatingcarriage 12, alternately trip a trip arm 72 for automaticallychangingthe'direction of the automatic movement of the carriage 12. Since 7construction for automatically-driving carriage 12' is' Conventional itis not further described, asit forms no 7 part of the invention per se.

In operation, a blade to beground is fastened to the blade holder insuch a manner that its upper flat surface a passes through the axis ofthe trunnions '16 and vprojects towards the path of rotation of wheel50.The carriage isthen moved to one position of itsreciprocation so thatthe working surface of wheel 50 is opposite one end of the workpiece A.a One of the upblade. p

The carriage is then moved to bring the other end of the blade oppositethe grinding wheel working surface andthe other upright is then adjustedaccording to the angle of bevel desired atthe other end of the blade. Asshown in Fig. 2, the outer end of track 28 is slightly lower than theinner end so that the right hand end of the work A will be given asharper angle of bevel than .the left-hand end, as seen in Fig. 2 and asindicated by the dotted line ground edge in Fig. 5, and as shown in thecompleted ground knife of Fig.6. V

The carriage is then set into automatic reciprocation whereupon thegrinding wheel may be moved by hand wheel '60 towards the projecting.blade to grind the edge surface.

' Inasmuch as the bearing surface of camtrack 28 is,

f a straight line, the amount of oscillation of the work 7 holder 20 isuniform per given unit of reciprocal movement of carriage 12 throughoutthe length of the blade 7 holder. e

rights 30 or 32 is then adjusted vertically for securing that angle ofbevel which is desired at that end of the V The grinding ,is continuedby advancing the grinding wheel by hand wheel 60 until the path ofrotation of whee1'50 reaches'the axisof trunnions 16, i. e. until thesurface being ground 0 has its upper edge lying exactly along that axis.If grinding is stopped at this point, the plane of the ground surface 0will then intersect 'the' top surface a of the work along a straightline cutting edge d '(Fig. 6)-but the angle of intersection of the twosurfaces will, because of the straight line uniform slope of track 28,vary uniformly from a wide angle e at one end to a sharper angle f atthe other end with the ground surface 0 being a warped surface, thuscreating that geometry A which features the novel cutting knifedescribed in the aforesaid co-pending application. 'Fig.;6, for purposesof clarity, exaggerates the difference in the two angles e and f. V I iIn the embodimentof the invention so far described and shown in Figs. 16inclusive, the rotation of the work holder20 'is'about an axis which isparallel to the path of transverse reciprocation of the carriage 12 andintersects the axis of the shaft 52 of grinding wheel.50. With thegrinding taking place at only one side of the wheel because of thebiasof the shaft 52'as hereinbefore' explained, the external cylindricalplane of revolution of the wheel 50 will intersect the blade A at thesame. angle no matter where the blade is in its transversereciprocation.

disc but offset relative to the radius so that it is tangent to a circlehaving as a center the axis of the chipper:

4 disc, as illustrated in Fig. 10, a certain refinement is desirable byway of varying the angle of grinding alongthe length of the cuttingedge. a It will be noted, as demonstrated in Fig. 11 where100 representsthe chipper disc center, that, in the c ase of the offset mounting, thetangentsto the paths of chipper revolution of successive points along,the cutting edge Z32 approachas a limit outwardly of the chipper disc aline normal to the projection of the cutting edge and as an inner limita line coincident with the projection of the cutting edge. Thesetangents, which represent the.

varying angle of attack, so to speak, at different points along thecutting edge intothe wood, thus progressively vary along the length ofthe cutting edge, increasing outwardly thereof. In order to make theangle of grind more nearly coincide with these varyingangles of .attack,I have found that I can readily vary the grinding angle over the lengthof the blade, by grinding with different arcsof the grinding wheel 50 atdifferent points along theblade. Thus, if I use at one'end ofthe blade asection of the wheel near the. top of the lower left-hand quadrant, asviewed in Fig. 2,1 may progressively decrease the angle of intersectionas the blade moves to the left so that nearits right-hand end, thecutting will be taking place near the bottom portion of the left-handlower quadrant of the grinding wheel as shown in Fig." 2. I do this bymounting the work holder 20 as shown in Fig. 7 so that its axis ofrotation is not parallel to its path of reciprocation but is inclinedrelative thereto. Thus, instead of having the fixed uprights 14 of Figs.1-6,

the trunnions 16a are mounted for limited universal movement'in blocks80 and take the form of studs journalled in crosswise rocker cylinders81, which, in

' in Fig. 7, it will be seen that the cutting at the left-hand end ofthe blade will be done at a higher section of the turn, are journalledin the blocks 80. Also, the blocks 80 are adjustablymounted in uprightslide guides -82 for vertical motion relative to the, base 10. Adjustingscrews 83 extend upwardly from the base in order tohold the slides 82 inadjusted position. The construction is identi- 1 calrat both sides ofthe machine. In a machine thus constructed and with the work holder axisof rotation in an inclined position asshown lower left-hand quadrant ofthe grinding wheel than the cutting at the right-hand end which, infact, will be at an angle which will be in a directionmore nearlyhorizontal, A blade so ground should have, by adjustment of the slope ofcam track 28, its largest angle of intersection of its cutting edgeforming surfaces at the left-hand end and its smallest angle ofintersection of its cutting edge forming surfaces at the right-hand end.When flipped end-to-end for mounting in the chipper disc of Fig. 10,

its right-hand end as seen inrFig. 7 will then be towards I the centerof the disc audits left-hand end as shown in Fig. 2 towards theperipheryof the disc, and with its cutting edge 102 tangent to a circlehaving, as a center,

the disc axis. As so mounted, the disc is designed to rotate in acounter-clockwise direction looking atthe face. of the disc, as in Fig..10.

In fact, the adjustment-of the relative heights of the revolution of thegrinding wheel 50 at its arc point of j grinding contact shouldintersect the axis of rotation of the. 1 work holder at any given pointalong said axis of work I holder rotation at'substantially the sameangle asithe angle which the tangent to the path of revolution of a.

pointalong the cuttingedge, when it is 'rotated on. a r0 tating disc,corresponding to the work holder'axis point, makes with the cuttingedgeV p j For example, Fig. 11 is an enlarged graphical representation ofone of the cutting blades shown in Fig. 10, the point 100 representingthe center of the chipper disc.

Because of the radial oifset of the cutting edge 102, the angle ofattack, so to speak, of the cutting edge 102 during counter-clockwiserotation of the disc, increases progressively outwardly of the cuttingedge 102; Thus, in Fig. 11, the tangents to the respective paths ofrevolution of the points 103, 104 and 105 are approximately 46, 52 and56.

What I attempt to do is to grind the blade at point 103 therealong witha point on the grinding wheel whose tangent plane intersects the cuttingedge 102 when it is in the work holder of the grinding machine as thegrinding is completed (i. e. the axis of work holder rotation) at anangle as nearly as possible the same as the 46 angle of Fig. 11; whereasfurther outwardly of the blade, as shown in Fig. 11 and more to theleft-hand of the blade, as shown in Fig. 7, I utilize a point on thegrinding wheel which is higher up on the left-hand lower quadrant of thegrinding wheel where the tangent plane to the grinding wheel pointintersects the work holder axis of rotation at a larger angle, namely52. This is accomplished by reason of the inclination of the work holderaxis of rotation in Fig. 7.

Fig. 12 shows a graphical method for determining the approximaterelative inclination of the work holder axis of rotation relative to ahorizontal plane through the axis of rotation of the grinding wheel 50for a particular disc mounting. For this purpose, one may lay out therelative geometry of the center of the chipper disc 100 and the locus ofthe cutting edge 102. A series of straight lines are then constructedfrom the center 100 to a series of points located along the cuttingedge. From the cutting edge points one then lays ofi on each of theconnecting lines the radius of the proposed grinding wheel which will beused and from these points one may draw the arcs 1-6 inclusive shown inFig. 12, the tangents of which at their intersection with the cuttingedge 102 will correspond respectively to the tangents of cutting edgepoints of attack in counterclockwise rotation of the disc. The locus ofthe arc centers is a curve of ever-decreasing slope shown in dottedlines in Fig. 12. A straight line 110 may thus be drawn approximatelythrough these centers and the angle a of its intersection with theprojection of the cutting edge 102 represents as an approximation theangle of inclination between the work holder axis and the horizontalplane through the axis of the grinding wheel which should be utilized inorder to procure the refined type of grinding hereinbefore described.

A diiferent form of work holder clamp for the blade is shown in Fig. 7,from that shown in Fig. 2, but since this forms no part of thisinvention, it need not be further described. The form of Fig. 2 may aswell be used in the refined version of the machine shown in Fig. 7.

Regardless, however, of whether this grinding refinement is introducedor not, the apparatus of this invention may be utilized in theproduction of new and improved chipper disc knives.

I claim:

1. Apparatus of the character described comprising a base, a carriagemounted on said base for reciprocation relative thereto, a work holdermounted on said carriage for rotation about one side of an axisextending in the direction of the path of reciprocation of saidcarriage, said work holder being adapted to hold a fiat-surfaced pieceof work with its flat surface lying in a plane passing through saidaxis, camming mechanism for rotating said holder about said axis as saidcarriage reciprocates, and a grinding wheel mounted on said base forrotation in a path disposed on the opposite side of said axis from saidwork holder and intersecting the plane of said fiat surface and formovement towards said work holder to move the path of wheel rotationtowards said axis of work holder rotation, and means for progressivelymoving said grinding wheel towards said work holder as said carriagereciprocates to grind the projecting edge of a piece of work so held insaid work holder until the path of rotation of said wheel passes throughsaid work holder axis, to provide a straight cutting edge for said pieceof work.

2. Apparatus of the character described comprising a base, a shaftmounted on said base for rotatably supporting a grinding wheel, a workholder mounted on said base and extending generally transversely of saidshaft, said work holder and shaft being mounted on said base for (a)relative reciprocation towards and away from each other, (b) transversereciprocation relative to one another, (0) rotation relative to oneanother about an axis extending in the direction of the path of saidrelative transverse reciprocation and interposed between said shaft andsaid work holder, said work holder being adapted to hold a flat-surfacepiece of work with its flat surface projecting therefrom towards, andlying in a plane intersecting, the path of rotation of a grinding Wheelcarried on the end of said shaft, camming mechanism for rotating saidwork holder and said shaft relative to one another about the said axisas they reciprocate transversely relative to one another and means forrelatively moving said work holder and shaft towards each other as theyreciprocate transversely to grind the edge of said work until the pathof rotation of the grinding wheel carried on said shaft intersects thefiat surface of the work at the said axis of relative rotation, toprovide a straight cutting edge for said piece of work.

3. Apparatus as claimed in claim 1, wherein the camming mechanismrotates the work holder to one extreme position of rotation as saidcarriage reaches one extreme position of reciprocation and to the otherextreme position of rotation as said carriage reaches the other extremeposition of carriage reciprocation.

4. Apparatus as claimed in claim 1, wherein said camming mechanismrotates said holder about said axis through the same angle of rotationfor each unit distance of work holder reciprocation whereby the anglewhich the surface ground on said piece of work makes with the flatsurface of the piece of work varies progressively uniformly along thelength of the work piece.

5. Apparatus as claimed in claim 1, wherein said camming mechanismincludes a cam track mounted on said base, a cam follower carried bysaid work holder resting on said cam track, said cam track beingconstituted of a straight bar extending in the same direction as thepath of carriage reciprocation, and means for independently varying theposition of both ends of said bar relative to the base to vary the slopeof said bar relative to said path of carriage reciprocation and hencethe amount of rotation of said Work holder in reciprocation of the camfollower therealong.

6. Apparatus as claimed in claim 1, wherein said Work holder issuspended from trunnions journalled on said carriage and wherein thecamming mechanism includes a cam follower extending from said workholder and resting on a cam track whereby the weight of said Work holdermaintains said cam follower against said cam track during reciprocationof said track for causing rotation of said work holder relative to saidcarriage.

7. Apparatus as claimed in claim 1, wherein the axis of rotation of thework holder is angularly inclined to the path of carriage reciprocation.

8. The method of grinding a knife blade having a straight cutting edgeadapted to be mounted on a disc for rotation during cutting with itscutting edge extending tangentially to a circle concentric with the axisof blade rotation, comprising grinding said blade with a rotatingabrasive surface and continuously and progressively varyin the angle ofintersection of the path of revolution of said abrasive surface with theblade along its cutting edge length substantially in accordance with thevarying angles which the tangents to the paths of revolution of eachpoints along the cutting edge make with ,said cutting edge when 'saidbladeiis rotated on said disc.

9. The method'of forming astraight knife edge having a Warped bevelledsurface comprising grinding a knife blade blanlcby reciprocatingsaid'blank backan'd forth across a transversely 'moving. abradingsurface while simultaneously oscillating the blank; initinied relationwith its reciprocal motion, about an axis lying along a surface of theblank inwardly offthe end ofthe blank which is being ground,progressively in one direction during reciprocal motion of the blank oneWay and progressively in a return direction during return reciprocalmosecte said axis.

References Cited in the' file of this patent UNITED STATES PATENTS 8Wolf etal. July 19, Abbott 'Feb. 10, Hamming May 26, Osterholm .Iu1y 24,Runshang Aug; 16, Jackson Nov. 19, Cornell Nov'. 15, Nicholas May 11,Monkle y l l Nov. 23,

FOREIGN PATENTS Great Britain 'July 2, Austria May 11, Great BritainJuly 7,

